The project involves the systematic investigation of adult age differences in the attentional components of cognition. Two series of experiments are proposed, each addressing one of the major aims of the project. The first aim is investigate the factors affecting adult age differences in controlled search (or controlled attention). Perceiver-controlled expectancy is examined using Posner's (1978) methods of mental chronometry. The second major aim of the project involves the relationship between visual attention and the structure of the human visual system. A series of experiments to test the transient channel loss hypothesis is planned. Factors affecting early light adaptation and contrast sensitivity are examined.